Method of forming an internally threaded, gasket-retaining cap



y 14, 1963 E. P. SUNDHOLM 3,089,161

METHOD OF FORMING AN INTERNALLY THREADED, GASKET-RETAINING CAP Filed Feb. 11, 1960 2 Sheets-Sheet 1 HIHHHII ll. H-h E I Q :4 (11% .t: I I Q I W N 1 PL Q 1]! W WNW gL Hlfi Ev k HUI J ATTORNEYS.

May 14, 1963 E. P. SUNDHOLM METHOD OF FORMING AN INTERNALLY THREADED, GASKET-RETAINING CAP Filed Feb. 11, 1960 2 Sheets-Sheet 2 ATTORNEYS.

United States Patent 3,889,161 METHOD OF FORMING AN INTERNALLY TI-HIEADED, GASKET-RETAINING CAP 1 Edwin P. Sundhoim, Albert City, Iowa Filed Feb. 11, 1960, Ser. No. 8,038 3 Claims. (Cl. 10-152) This invention relates to a method of forming an internally threaded, gasket-retaining cap. The method is particularly advantageous for the manufacturing of dispensing head caps for cartridge-loading grease guns.

In my copending application, Serial No. 785,689, filed January 8, 1959, now U.S. Patent No. 3,059,819, there is described a grease gun which is adapted for use with both cartridge-packaged greases and bulk-filled greases. Heretofore the caps for the dispensing heads of this type of grease gun have been provided with internal threads by means of a conventional thread cutting tool, which cuts the threads by removing the metal in the usual way. To assure a seal between the forward end of the grease gun barrel and the inside of the cap, it has been the practice to utilize a gasket or washer which is received within the cap and held in place by the inwardly crimped forward end of the grease gun barrel. When cartridgepackaged greases are employed, however, the inward crimping of the grease gun barrel is not particularly desirable since it tends to hold the outer walls of the cartridge away from the inner Walls of the grease gun barrel. But if the crimp is eliminated, diificulties are encountered because the gasket tends to become unseated and to work itself into the forward end portion of the grease gun, especially when the gun is being used alternately with bulk-filled greases and cartridge-packaged greases. What is needed is some means of positively retaining the gasket within the cap, but it is not feasible to machine a groove within the cap either prior to or subsequent to the threading operation.

It is therefore a principal object of this invention to provide a method of forming grease gun caps which are adapted for use with guns using cartridge-packaged greases. More specifically, it is an object of the present invention to provide a method of forming internallythreaded, gasket-retaining caps which can be employed for such grease guns or for other purposes. Further objects and advantages will be indicated in the following detailed specification.

The invention is shown in an illustrative embodiment in the accompanying drawings, in which FIGURE 1 is a side elevational view of an apparatus which can be employed in practicing the method;

FIGURE 2 is a front view of a cylindrical metal piece from which the cap can be formed, the view showing the closed end of the piece;

FIGURE 3 is a side sectional view of a metal piece like the one of FIGURE 2 and showing a portion of a mandrel inserted within the open end of the piece, the piece and mandrel being shown as they would appear when the mandrel is first inserted;

FIGURE 4 is an enlarged side elevational view showing certain components of the apparatus of FIGURE 1 in section, and illustrating the way in which the cylindrical metal piece of FIGURES 2 and 3 is formed into an internally threaded, gasket-retaining cap;

FIGURE 5 is a view similar to FIGURE 3 showing the cap as it is removed from the mandrel, both the mandrel and cap being shown in section; 7

FIGURE 6 is a front view of the completed cap; and,

FIGURE 7 is a side sectional view of the cap of FIG- URE 6, showing the gasket in place within the cap.

Looking first at FIG. 1, the cylindrical metal piece from which the cap is to be formed is indicated in dotted lines and by the reference number 10. The mandrel 11 "ice is also indicated in dotted lines. This view also illustrates the relationship of the piece 10 and the mandrel 11 to the rollers 12 which are disposed around the projecting or free end of mandrel 11. It will be understood that the apparatus of FIG. 1 is merely being shown as an illustration of one type of apparatus which can be used in connection with the method of this invention.

The cylindrical metal piece 10 is shown in greater detail in FIGS. 2 and 3. The piece has smooth side walls 13 and one closed end 14 since the cap to be formed from piece 10 is intended for use as part of the dispensing 'head of a grease gun, the piece is provided with a point projection 15 and a ring projection 16 for use in attaching the cap to the high pressure cylinder as described in greater detail in my Patent 2,436,701. There is also provided a raised portion 17 for use in mounting a grease gun filler fitting.

In the first step of the method, as shown more clearly in FIG. 3, the metal piece 10 is positioned on the outer free end of the cylindrical mandrel 11. The projecting end portion of mandrel 11 is provided with a threaded band 18. As will be noted, band 18 is adjacent the free end of mandrel 11. Preferably band 18 is spaced inwardly from the free end. In the illustration given, a smooth surfaced annular portion 19 is provided between threaded band 18 and the end of mandrel 11, the portion 19 having an external diameter not greater than the deepest cut portion of band 18, that is, the diameter measured across the mandrel between the roots of the threads.

The correct initial positioning of the cap 19 in relation to the mandrel 11 is shown in FIG. 3. As shown there, the positioning should be such that the closed end 14 of the piece 10 abuts the free end of the mandrel with the threaded band 18 being opposite the innermost portion of the side walls 13. To accomplish this positioning, it will be apparent that the projecting end portion of mandrel 11 including threaded band 18 must have a slightly smaller maximum external diameter than the internal diameter of the cylindrical walls 13. In other words, as shown in FIG. 3, the piece 10 will be loosely received on mandrel 11. As previously indicated, the extreme outer end portion 19 of the mandrel is preferably unthreaded, and will be spaced inwardly from the adjacent surfaces of walls 13.

The next step in the method is shown in FIG. 4. In this step rollers, such as rollers 12, are applied to the outside of the innermost portion of side walls 13 to force this portion of the side wall against the threaded band 18. In practicing the method of this invention, it is essential that the application of the rollers begins at an inwardly spaced distance from the free end of mandrel 11, as indicated in FIG. 1 and shown more clearly in (FIG. 4. In the illustration given, the rollers 12 are provided centrally with an annular recess 20, and an outwardly projecting end portion 21. In carrying out the method, the projecting roller portion 21 is aligned with the threaded band 18 of the mandrel, while the unthreaded end portion of mandrel 11 is positioned opposite roller recess 20.

When the rollers 12 are applied in the manner just described, the application of the rollers begins at an inwardly spaced distance from the free end of the mandrel. In this way, the portion of side walls 13 adjacent the free end of mandrel 11 remain spaced from the mandrel, as indicated in FIG. 4 at 22.

In order to completely form the threads on the inside of side wall 13, in accordance with known procedures, the mandrel 11 and the rollers 12 will be rotated relative to each other about the axis of the mandrel. For example, in the illustration given, mandrel 11 remains stationary while head 23, upon which the rollers 12 are mounted, revolves about a central axis coinciding with the axis of mandrel 11. The rollers 12. are also free to rotate about their own individual axes. Through a hydraulic-mechanical mechanism (not shown) rollers 12 can be moved inwardly and outwardly with respect to man-drel 11. During the forming operation, as will be understood, the rollers 12 will be forced inwardly against the mandrel as they rotate around the mandrel.

It has been found that the method produces best results when the closed end 14 of the piece is held in fixed relation to the free end of mandrel 11 during the thread rolling operation. In the illustration given, this is accomplished by clamping end 14 against the end of the mandrel. As shown more clearly in FIG. 4, a holding piece 24 provides a face which is shaped to engage the outer face of the closed end 14 of piece 10. End wall 14 can be clamped between the end face of holding piece 24 and the free end of mandrel 11 in any suitable (way. In the illustration given, the portion of the free end of the mandrel which opposes the face of holding piece 24 is provided by an axially-shiftable slide 25. Through a mechanical cam arrangement (not shown) actuated by a compressed air cylinder (indicated generally at 26 in FIG. 1) slide 25 can be moved into and out of clamping engagement with the inner surface of the wall 14 of piece 10. In FIG. 4, slide 25 is shown in its outer position with the piece 10 clampingly engaged. In FIG. 5, the slide 25 is shown in its retracted position. It will be understood that holding piece 24 should be mounted within head 23 so that it can remain stationary while head 23 rotates.

The construction of slide 25, and its method of actuation is more completely described in my copending application Serial No. 8,039, filed February 11, 1960, entitled, Internal Thread Rolling Mandrel.

In order to maintain the relative positions of the mandrel 11 and the side walls 13 of the piece 10 during the rolling operation, it is desirable to rotate rollers 12 around mandrel 11 in a direction causing piece 10 to tighten on mandrel 11 as the threads are formed. For example, if the threads being formed are right-handed threads, rollers 12 would rotate around mandrel 11 in a clockwise direction as viewed in a direction looking toward the free end of the mandrel. In other words, during the thread forming, the piece 10 would not resist the clamping engagement whereby it is held against the end of mandrel 11, but instead would tend to force itself even more firmly against the free end of the mandrel, much as if an already threaded cap were being screwed onto the threaded portion of the mandrel.

In FIG. 5, the piece 10 is shown being unscrewed from the threaded portion of mandrel 11 after the cap has been completely formed. Once the clamping engage ment between the free end of mandrel 11 and the inside of wall 14 has ben released, the completed cap can readily be unscrewed.

The completed cap C is illustrated in FIGS. 6 and 7. As shown more clearly in FIG. 7, the cap is now provided with internal threads 27 and with an annular groove 28, which is adapted for receiving a gasket, such as gasket 29. The annular groove 28 is adjacent the inside of end wall 11-4, and the internal diameter of the threaded portion 27 of the cap is substantially smaller than the internal diameter of the grooved portion 28. Consequently, the gasket '29 once having been snapped into place, as can easily be done by using a resilient rubber gasket, will remain securely in place until it becomes so worn as to require replacing.

As will be apparent to those skilled in the arts of metal forming, the method of this invention is applicable to caps formed of a variety of metals, such as steel, brass, copper, aluminum, etc. For forming grease gun caps, a cold rolled steel is preferred, such as cold rolled strip steel, aluminum killed, temper 5.

While the method of this invention has been described in relation to a specific preferred embodiment, and many details have been set forth in the foregoing specification, it will be apparent to those skilled in the art that the method is not limited to the specific embodiment set fort herein.

I claim:

1. The method of forming an internally threaded cap from a cylindrical metal piece having smooth side walls and one closed end, comprising positioning said metal piece on a cylindrical mandrel having an outer free end portion providing a threaded band thereon, the crest diameter of said band being only slightly less than the internal diameter of said piece, said positioning being such that the portion of said side walls adjacent the open end of said piece is opposite said band, holding said closed end against movement toward said mandrel, applying continuous radial pressure by means of smooth faced rollers at circumferentially spaced locations on the outside of the said portion of said side walls adjacent said open end, simultaneously rotating said rollers relative to said side walls in such a direction as to effect tightening of the piece on said mandrel and thereby swaging internal threads in said side walls by forcing the said portion of said side walls against said band, the application of said rollers beginning at an inwardly spaced distance from the closed end of said piece and said application reducing the diameter of said piece around said threaded band while the portion of the side walls of said piece immediately adjacent the closed end thereof maintains an internal diameter of at least slightly greater than the crest diameter of said band, the exterior of the said portion of said walls adjacent the open end of said piece remaining smoothsurfaced, releasing said radial pressure, and removing the completed piece by rotating said piece on said mandrel in such a direction as to effect unthreading from said mandrel.

2. The method of forming an internally threaded cap from a cup-shaped metal piece having a cylindrical side wall, a transversely extending end wall, and an open end, comprising positioning said piece upon the free end portion of a cylindrical mandrel providing a threading band, said free end portion extending through the open end of said piece and the portion of said side wall adjacent said open end being opposite said band, the crest diameter of said band being only slightly less than the internal diameter of said side wall, holding the inside surface of said closed end against movement toward said mandrel, applying continuous radial pressure against the outer surface of the said portion of said piece opposite said threaded band by means of rollers at a plurality of circumferentially spaced locations to reduce the diameter of said portion opposite said band, said radial pressure being applied along lines parallel to the outer surface of said cap and extending from said open end up to a position spaced from said closed end without applying said pressure to the portion of said side wall immediately adjacent said closed end, simultaneously rotating said rollers relative to said piece in such a direction as to effect tightening of the piece on said mandrel and thereby swaging internal threads in said side wall, releasing said radial pressure, and removing the completed piece by rotating said piece on said mandrel in such a direction as to effect unthreading from said mandrel.

3. The method of forming an internally threaded gasket-retaining cap from a cup-shaped metal piece having a cylindrical side wall, a transversely-extending end wall, and an open end, comprising positioning said piece upon the free end portion of a cylindrical mandrel providing a threading band, said free end portion extending through the open end of said piece and the portion of said side wall adjacent said open end being opposite said band, the crest diameter of said band being only slightly less than the internal diameter of said side wall, said positioning being such that the portion of said side wall immediately adjacent said end wall extends outwardly beyond the outer end of said threading bands, holding the inside surface of said closed end against movement to wards said mandrel, applying continuous radial pressure against the outer surface of the said portion of said piece opposite said threading hand by means of rollers at a plurality of circumferentially spaced locations, said radial pressure being applied along lines parallel to the outer surface of said cap and extending from said open end out to a position spaced from said closed end without applying said pressure to the portion of said side wall immedirollers relative to said piece in such a direction as to effect tightening of the piece on said mandrel and thereby swaging internal threads in said side Wall, releasing said radial pressure, and removing the completed piece by rotating said piece relative to said mandrel in such a direc- 5 tion as to effect unthreading from said mandrel.

References Cited in the file of this patent UNITED STATES PATENTS 

1. THE METHOD OF FORMING AN INTERNALLY THREADED CAP FROM A CYLINDRICAL METAL PIECE HAVING SMOOTH SIDE WALLS AND ONE CLOSED END, COMPRISING POSITIONING SAID METAL PIECE ON A CYLINDRICAL MANDREL HAVING AN OUTER FREE END PORTION PROVIDING A THREADED BAND THEREON, THE CREST DIAMETER OF SAID BAND BEING ONLY SLIGHTLY LESS THAN THE INTERNAL DIAMETER OF SAID PIECE, SAID POSITIONING BEING SUCH THAT THE PORTION OF SAID SIDE WALLS ADJACENT THE OPEN END OF SAID PIECE IS OPPOSITE SAID BAND, HOLDING SAID CLOSED END AGAINST MOVEMENT TOWARD SAID MANDREL, APPYLING CONTINUOUS RADIAL PRESSURE BY MEANS OF SMOOTH FACED ROLLERS AT CIRCUMFERENTIALLY SPACED LOCATIONS ON THE OUTSIDE OF THE SAID PORTION OF SAID SIDE WALLS ADJACENT SAID OPEN END, SIMULTANEOUSLY ROTATING SAID ROLLERS RELATIVE TO SAID SIDE WALLS IN SUCH A DIRECTION AS TO EFFECT TIGHTENING OF THE PIECE ON SAID MANDREL AND THEREBY SWAGING INTERNAL THREADS IN SAID SIDE WALLS BY FORCING THE SAID PORTION OF SAID SIDE WALLS AGAINST SAID BAND, THE APPLICATION OF SAID ROLLERS BEGINNING AT AN INWARDLY SPACED DISTANCE FROM THE CLOSED END OF SAID PIECE AND SAID THREADED BAND WHILE DIAMETER OF SAID PIECE AROUND SAID THREADED BAND WHILE THE PORTION OF THE SIDE WALLS OF SAID PIECE IMMEDIATELY ADJACENT THE CLOSED END THEREOF MAINTAINS AN INTERNAL DIAMETER OF AT LEAST SLIGHTLY GREATER THAN THE CREST DIAMETER OF SAID BAND, THE EXTERIOR OF THE SAID PORTION OF SAID WALLS ADJACENT THE OPEN END OF SAID PIECE REMAINING SMOOTHSURFACED, RELEASING SAID RADIAL PRESSURE, AND REMOVING THE COMPLETED PIECE BY ROTATING SAID PIECE ON SAID MANDREL IN SUCH A DIRECTION AS TO EFFECT UNTHREADING FROM SAID MANDREL. 